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Date: Fri, 18 Sep 2026 13:43:42 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: paulmck@kernel.org
Cc: Breno Leitao <leitao@debian.org>, Hugh Dickins <hughd@google.com>,
 Baolin Wang <baolin.wang@linux.alibaba.com>, linux-mm@kvack.org,
 linux-kernel@vger.kernel.org, kernel-team@meta.com, stable@vger.kernel.org
Subject: Re: [PATCH] mm/shmem: report RCU-tasks quiescent states while
 undoing a range
Message-Id: <20260918134342.c50423cfe3b2910e899226f2@linux-foundation.org>
In-Reply-To: <a67e8b91-ebc2-4d3d-b6ea-d221b297fad0@paulmck-laptop>
References: <20260918-shmem-tasks-rcu-v1-1-79acf91a2569@debian.org>
	<20260918123239.8f25b984ca280fcc11ef6e6a@linux-foundation.org>
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On Fri, 18 Sep 2026 13:24:53 -0700 "Paul E. McKenney" <paulmck@kernel.org> wrote:

> > 
> > > --- a/mm/shmem.c
> > > +++ b/mm/shmem.c
> > > @@ -1367,7 +1367,7 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, uoff_t lend,
> > >  		}
> > >  		folio_batch_remove_exceptionals(&fbatch);
> > >  		folio_batch_release(&fbatch);
> > > -		cond_resched();
> > > +		cond_resched_tasks_rcu_qs();
> > 
> > Won't this change remove the cond_resched() function from old kernels
> > which really want it?
> 
> The cond_resched_tasks_rcu_qs() macro implies cond_resched():
> 
> 	#define cond_resched_tasks_rcu_qs() \
> 	do { \
> 		rcu_tasks_qs(current, false); \
> 		cond_resched(); \
> 	} while (0)
> 

Oh, should've looked.

And it appears to have been this way forever, so
s/cond_resched/cond_resched_tasks_rcu_qs/ won't break old kernels.